In the production of gypsum board, an aqueous core slurry composed predominantly of calcined gypsum (stucco) is spread between two sheets of paper and the resultant core is allowed to set by rehydration of the stucco and followed by driving away the excess water by heating the gypsum board in a dryer. In order to decrease the density of the gypsum core, it is common practice in the industry to incorporate air bubbles in the core. This is normally achieved by the addition of a pregenerated foam to the stucco mixer, along with other additives immediately prior to core formation. This foam is normally generated by incorporating air in an aqueous solution of foaming agent in a foam generator. Considerable quantities of water, known as gauging water are added to the stucco slurry to render the core slurry adequately fluid. The water in excess of that required to rehydrate the stucco is subsequently removed from the set gypsum board in the dryer. Minimizing the energy consumption in the dryer is a general objective in the industry, which is limited by the quantity of gauging water required to obtain an adequately fluid slurry.
It is therefore the object of this invention to provide a means of producing gypsum board, whereby savings of energy may be effected.